Control system for suction dredge relief valve



D. L. HOFER July 17, 1956 CONTROL SYSTEM FOR SUCTION DREDGE RELIEF VALVEFiled March 13, 1953 United States Patent CONTROL SYSTEM FOR SUCTIONDREDGE RELIEF VALVE David L. Hofer, Berkeley, Calif.

Application March 13, 1953, Serial No. 342,257

1 Claim. (Cl. 10311) The present invention is directed to, and it is amajor object to provide, a novel control system for hydraulicallyopening the relief or water entry valve on the intake pipe of a suctiondredge upon, and for the purpose of relieving, abnormal Workingconditions prevailing in the pumping line of the dredge.

Upon the occurrence of abnormal Working conditions, such as a slug orplug occurring at the outer end of the intake pipe or gassy materialbeing encountered thereby,'or the discharge pipe loading up, it isrequisite that the relief valve on the intake pipe be opened so thatwater in substantial quantity may freely enter the pumping line torelieve such abnormal working conditions and prevent damage which mightotherwise occur.

I have ascertained that when such abnormal working conditions exist inthe umping line, the electrical load on the energizing circuit for theelectric motor which drives the dredge pump, is materially reduced.

' It is therefore another important object of the invention to provide acontrol system, for the relief valve, which automatically responds tosuch a drop in the electrical load and opens said relief valve.

It is also an object of the present invention to provide a controlsystem, for the purpose described, which is designed for ease andeconomy of initial installation, and positive and effective operationwithout manual attendance by the operator.

Still another object of the invention is to provide a practical andreliable control system for a suction dredge relief valve, and one whichwill be exceedingly effective for the purpose for which it is designed.

These objects are accomplished by means of such structure and relativearrangement of parts as will fully appear by a perusal of the followingspecification and claim.

The figure of the drawing is a diagrammatic illustration of the novelcontrol system.

Referring now more particularly to the characters of reference on thedrawings, the control system is adapted to be embodied in a suctiondredge which includes a dredge boat 1 which supports a pump 2 drivenfrom an electric motor 3 by an endless drive unit 4; the electric motor3 being energized from a circuit, indicated at 5.

An intake pipe 6 leads from an under-water point to the pump 2, and thelatter includes a discharge pipe 7 which is adapted to couple to thepipe line which leads to the waste area.

Adjacent but above the outer end 8 of the intake pipe 6, the latter isfitted with a normally closed butterfly type relief valve 9; opening ofsuch relief valve permitting water in substantial quantity to rushfreely into the intake pipe 6 for the purpose of relieving theaforementioned abnormal working conditions.

The relief valve 9 includes a radial arm 10 pivotally connected, at itsouter end, to a longitudinal rod 11 which extends upwardly above andparallel to the intake pipe 6.

At its upper end the connecting rod 11 is attached to the lower end ofthe piston rod 12 of a fluid pressure actuated power cylinder 13 mountedlengthwise in connection with said intake pipe 7, preferably at anabovewater point and in position such that the rods 11 and 12 are inalinement.

A piston 14 is disposed in the power cylinder 13 intermediate the endsof the same and in connection with the piston rod 12; there being aloaded compression spring 15 surrounding said piston rod 12 between thepiston 14 and the lower end of the power cylinder 13. The spring 15urges the piston 14 in a retracting direction, which is the direction ofmovement to open the relief valve.

At its upper end the power cylinder 13 is in communication with atwo-position valve 16; such valve when in one position, as shown in thedrawings, establishing communication between an air pressure supply 17,and when in another position (not shown) blocking off the conduit 17 andestablishing communication between the power cylinder 13 and a vent port18.

When the valve 16 is in the position shown, and at which time theconduit 17 is in communication with the power cylinder 13, the resultantair pressure in said cylinder works against the piston 14, maintainingit advanced against the spring 15 and holding the relief valve 9 closed.However, when the valve 16 is actuated to a position blocking. conduit17, the power cylinder 13 vents through port 18, whereupon the spring 15acts to retract the piston 14 and open the relief valve 9.

The novel control system, which embodies the essence of the presentinvention, comprises the following:

The valve 16 is normally maintained in the position establishingcommunication between conduit 17 and power cylinder 13, by means of anenergized solenoid 19; such solenoid being energized by a circuit 20drawing from a suitable source of current.

A normally closed adjustable electro-responsive circuit breaking unit21, such as a wattmeter or other loadresponsive instrument which can bepurchased on the open market, includes normally closed contacts 22forming a switch interposed in the circuit 20. The opening of thecontacts 22 is controlled by the functioning of the instrument 21 upon areduction of the load on the motor as indicated by the wattmeter.

A transformer 23 is connected into the energizing circuit 5 ahead of theelectric motor 3, and a feed circuit 24 leads from the transformer 23 tothe input terminals of the electro-responsive circuit breaking unit 21.The working or actuating mechanism of said circuit breaker is energizedby another circuit 25 which leads from the circuit 5; there being avoltage reducing transformer 26 in the circuit 25.

The above described control system functions as follows:

When the pumping line of the dredge, including the pump 2, is undernormal working conditions, the electrical load on the circuit 5 isrelatively heavy; the contacts 22 then being adjusted so as to remainclosed.

In turn this causes the solenoid 19 to stand energized, holding thevalve 16 in the position which loads the power cylinder 13, maintainingthe relief valve 9 normally closed.

However, upon an abnormal working condition occurring in the pumpingline of the dredge, the load on the electric motor 3, and consequentlythe electrical load on the circuit 5, substantially reduces. When thisoc curs lesser current is fed by circuit 24 to the circuit breaker unit21, resulting in the contacts 22 being opened.

This breaks the circuit 20, and solenoid 19 is deenergized, moving thevalve 16 to its power cylinder venting position. As soon as the powercylinder 13 vents, the spring 15 retracts the piston 14 and the reliefvalve 9 is opened, whereupon water rushes freely into the pumping lineto relieve the abnormal working condition.

With the described control system, the relief valve on a suction dredgeis automatically opened whenever the necessity arises, and automaticallyclosed when the abnormal working condition is alleviated.

At certain times the operator might desire to open the relief valve 9independently of the automatic control, and this is accomplished by theuse of a manual or foot switch 27 interposed in the circuit 20 in serieswith the circuit breaker 21; the switch 27 normally being closed.

With a control system as described the suction dredge works withincreased efiiciency, safety, and yardage, yet with a nominal initialcost of the system, and practically no maintenance thereafter required.

From the foregoing description it will be readily seen that there hasbeen produced such a system as substantially fulfills the objects of theinvention, as set forth herein.

While this specification sets forth in detail the present and preferredconstruction of the system, still in practice such deviations from suchdetail may be resorted to as do not form a departure from the spirit ofthe invention, as defined by the appended claim.

Having thus described the invention, the following is claimed as new anduseful, and upon which Letters Patent are desired.

In a suction dredge which includes a pipe line having a normally closedrelief valve connected thereto intermediate its ends and arranged whenopen to admit water into the line, an electric motor driven pump in thepipe line, an energizing circuit for the electric motor, power mechanismadapted to open said relief valve, a fluid pressure control valvemovable from one position to another position to then cause said powermechanism to open the relief valve, and an electric device to so movethe valve; an automatic control system for said relief valve comprisinga control circuit connected to the electric device of said controlvalve, a switch interposed in the control circuit and having open andclosed positions, an electric-load responsive instrument, a feed circuitconnecting the energizing circuit and said instrument, and means an theinstrument and switch to cause the latter to move from one position tothe other upon the ioad in the energizing circuit and reflected in theinstrument, dropping below a predetermined normal to then place thecontrol circuit in condition so that the electric device moves thefluid-pressure control valve from said one position to the otherposition.

References Cited in the file of this patent UNITED STATES PATENTS1,562,561 Horter Nov. 24, 1925 1,773,963 Deutsch Aug. 26, 1930 1,783,036Crawford Nov. 25, 1930 2,572,263 Hofer Oct. 23, 1951 2,644,400 HoferJuly 7, 1953 2.687,693 Hudson Aug. 31, 1954

